Question

Doar "d", va rog, este urgent ​

Answer 1

Răspuns:

f(x) =2x-16

Explicație pas cu pas:

a*(-1) +b=-18

a*4+b=-8

scadem  pe prima din a doua

5a=10

a=2

b=-18+a=-18+2=-16

f(x) =2x-16, care verifica

Answer 2

$\it d)\ \ f:\mathbb{R}\ \longrightarrow\ \mathbb{R},\ \ f(x)=ax+b\ \ \ \ (1)\\ \\ A(-1,\ -18)\in Gf \Rightarrow f(-1)=-18 \stackrel{(1)}{\Longrightarrow}\ -a+b=-18 \Rightarrow b=a-18\ \ \ \ (2)\\ \\ B(4,\ -8)\in Gf \Rightarrow f(4)=-8 \stackrel{(1)}{\Longrightarrow}\ 4a+b=-8 \Rightarrow b=-4a-8\ \ \ \ (3)$

$\it (2),\ (3) \Rightarrow a-18=-4a-8 \Rightarrow a+4a=-8+18 \Rightarrow 5a=10 \Rightarrow a=2\ \ \ \ \ (4)\\ \\ (2),\ (4) \Rightarrow b=2-18 \Rightarrow b=-16\ \ \ \ \ (5)\\ \\ (1),\ (4),\ (5) \Rightarrow f(x)=2x-16$